Gunfire control computer



(xwbkst July 9, 1946.l

G. A. cRowTHER GUNFIRE CONTROL COMPUTER Fi 1ed April 2, 1941 No YM 2 Sheets-Sheet l v IN VEN TOR George A Crowlwr Z@ www.

ATTORNEY Juf RUJI i EDG:

July 9, 1946- G. A. cRowTHr-:R

GUNFIRE CONTROL COMPUTER 'Filed April 2, 1941 2 sheets-sheet 2 IN VEN TORl GeoyeA Crowther BY gow/Cv!" A TTORNE Y UJI HUJI l Enit.

Patented July 9, 1.946

GUNFIRE CONTROL COMPUTER George A. Crowther, Manhasset, N. Y., assigner to Ford Instrument Company, Inc., Long Island City, N. Y., a corporation of New York Application April 2, 1941, Serial No. 386,451

2 Claims. l

This invention relates to gun-lire control computers and particularly to that type of computers used to control the ring of guns against aircraft.

The problem of the control of gun-lire against aircraft may be divided into two classes; (l) where the aircraft or target is approaching directly towards its objective or the point of observation and the firing gun, and (2) where the target is passing at a distance to one side or the other of the observing and firing point. The invention herein disclosed is applied to the rst mentioned class. It will of course be understood that some of the principles thereof are applicable to the solution of problems of the second mentioned class.

InA considering the solution of the problem of anti-aircraft re control to which this invention is applied as one embodiment thereof, it is assumed that the target is directly approaching its objective, which is the point of observation and the point of firing of the gun, at a substantially constant height above the horizontal plane of the objective, such as would be done in horizontal-bombing of a selected point. Upon the picking up of the target by observers at the objective, the slant range of the target and its elevation above the horizontal, expressed in angular units, are observed by instruments well known in the art and from the observed data the height of the target and the horizontal range may be determined, or if the height of the target is known or obtained by observations and the elevation is observed, the slant range and the horizontal range may be determined.

From experimental data obtained during target practices, the most effective ranges of the guns .are known as well as the time in seconds required to set and adjust the sights and the fusesof the projectiles and to load and fire the projectiles. In this specification, the time required to set the observed values into the mechanisms, for the mechanisms to calculate the advance range and the corresponding values of deflection and sight angle, and the time required to adjust the sight and gun and load and fire the gun is defined as the preparation period of timeij This preparation period is arbitrarily selected and is based upon experience under various circumstances of operation.

Fundamentally an vobject of this invention is to provide a graphic solution of this problem. More especially the invention aims to provide a relatively simple and easily operable chart mechanism into which the problem may be quickly and progressively introduced to afford a graphic representation thereof, and which will automatically actuate visual indicators of the needed quantities for the proper setting of a gun under the represented conditions. Other objects and advantagesof the invention will appear from. the particular description hereinafter.

For the attainment of these objects the invention comprehends a fixed charton which are delineated polar and rectangular coordinates and in relation to which move a vector arm pivoted at the polar point and component slides adjustable parallel to the rectangularcoordinates which` intersect at the polar point. The polar coordinates represent the direct or slant range and the elevation angle of an observed target, and the rectangular coordinates represent the vector components of height and horizontal range. It is obvious that with any two of these values given the other two will automatically develop from the setting. lThe chart also has delineated thereon trajectory and time of flight curves for reasons which will hereinafter appear.

Preferably in accordance with the invention the movable elements are settable manually in accordance with scale indications, and to facilitate the location of resultant points on the chart the component slidesv will preferably carry cross wires. Computing means may be selectively associated with the horizontal component slide to expedite the introduction of future positions of an observed target, the association preferably being such that the act of computation will at the same time reset the slide in accordance with A the computation.

The invention also comprehends means for translating'the angular movement of the vector arm during a setting to introduce a future or predicted position of the target into terms of gun setting relative to the line of sight from the gun to the target, and for visually indicating these quantities. i

Mechanisms for accomplishing the objects of the invention and their operation will be understood by considering the following description and accompanying drawings in which:

Fig. 1 is an elevation side view of an aircraft target directly approaching an observing and ring point at a constant height and showing the consecutive angular and linear relations of the target to the observing and ring point;

Fig. 2 is a view of achart and associated mechanism embodying the invention for graphically operating positions of the mechanism of Fig. 2.

Referring particularly to Fig. 1, an aircraft or target I is directly approaching the observing and firing point O at a constant height (H) above the horizontal O-O and at a horizontal speed of St.

When the target I reaches point A, observers at O observe the slant range (R) and the elevation angle of the target (AI), from which the height (H) and the horizontal range (RH) may be calculated by the equations resulting from the right angle triangle OAA of H =R sin AI and RH :R cos AI, respectively. A' is the projection of the point A on the horizontal O-O'.

The distance AB represents the distance traveled by the target during the preparation .period of time (X), and determines the position of the point B at which the target I will be at the end of the preparation period. The value of the distance AB is determined as the product of the preparation period (X) and the target speed (St) and may be expressed by the equation The horizontal range of target I at point B (BH3) is equal to the observed horizontal range minus the distance AB or From the right angle triangle OBB', the elevation of the target when at point B (A3) will be the angle Whe tangent is the height divided by the horizontal range to the point B, or

.A3-tan 1RH3 (3) As is well known the time of flight (t) is the period of time between the instant of firing of the projectile and the instant of its intercepting the target. The travel of the target during this period of time is equal to the speed of the target multiplied by the time of flight or t-St, and is indicated on Fig. 1 by the line BC, or

This distance determines the point of intercept (C) and a perpendicular dropped from C determines the point C. It is obvious that OC represents the horizontal range to the point of intercept (RHZ) and that The elevation angle of the point of intercept (A2) is obtained from the right angle triangle OCC and is theV angle whose tangent is the height divided by the horizontal range to the point of intercept (BH2) or A2-tan 1RH2 (6) The elevation of the gun above the line of sight to the point B, to allow for the movement of the target during the time of Hight is known as vertical angular deflection (Ut) and may be expressed as The correction in elevation, known as super elevation (e), that must be applied to compensate for the shape of the trajectory of the projectile, is known for various combinations of horizontal ranges and heights and is obtained in the operation of this mechanism from the trajectory chart associated with the vector analyzer. The total elevation of the gun above the line of sight is known as sight angle (Us) and may be expressed as Referring particularly to Fig. 2, the vector analyzer 2 comprises a vector arm 3 and a pair of component slides 4 and 5, respectively, all superimposed on a trajectory chart 6.

The vector arm 3 is pivoted at the point 1 and is graduated along one edge in terms of slant range (R), the zero graduation being at the point 1. The arm 3 terminates in a pointer 8 in line with the edge of the arm carrying the range graduations. The pointer 8 is read against the angular elevation scale 9 to indicate the angular .position of the arm 3. A toothed sector I0 is secured to the anm 3 and the arm is thereby positioned by gears II which are connected to a wide face gear I2. The gear I2 meshes with a narrow face -gear I3 mounted on a shaft I4, which is rotatably positioned by a knob I5.

The trajectory chart' includes a horizontal range (RH) scale I 6 across the bottom and a height (H) scale I1 along the left side. These scales represent the rectangular coordinates of the chart and the zero graduation of each scale is at the pivot point 1 of the vector arm 3. The spacing of the .graduations of the horizontal range scale is the same as that of the range (R) scale on the vector arm 3. The height scale is graduated in feet to the same scale as the range graduations which is in yards and therefore the height graduations are spaced at one-third the distance apart of the graduations of the range scales. The range scales are numbered in thousands of yards and the height scale in thousands of feet.

Radial lines I8 extending to the angular elevation scale 9 represent polar coordinates of the chart 6 and are used in locating the vector arm 3. Trajectory curves I9 represent the path of the projectile for various gun elevations. Time of flight curves 20 indicate the points the projectile Will reach along its Various trajectories in the number of seconds indicated by the time of flight (t) scale 12| at the left of the chart. In Fig. 2 several curves of each form are shown for purpose of illustration but in the chart as actually used more curves of each type may be provided as desired.

The horizontal range component slide 4 is provided vvith a stiff vwire or index 22 projecting perpendicular to the direction of movement of the slide 4 and the height component slide 5 is provided with a similar wire or index 23 extending perpendicular to its direction of movement. Both of these wires project over the trajectory chart B.

The height component slide 5 is positioned by a knob' 24, a shaft 25 and gears 26 meshing with a rack 21 on the slide 5. The slide 5 is restrained to movement parallel to the height scale by guides (not shown)`.

The horizontal range component slide 4 is positioned by a knob 28 on shaft 29 which carries a narrow face gear 30. 'I'he narrow face gear 30 meshes with a wide face gear 3| on a shaft 32 which drives shaft 33 by gears 34. The shaft 33 is geared to rack 35 on slide 4 by gears 36. The slide 4 is restrained to movement parallel to the horizontal range scale by guides (not shown).

The end of shaft 33 carries one-half of a clutch 31, the other half of which is slidably mounted on the shaft of a gear 38 and is pressed into contact with the first half .by a spring 33. The clutch 31 is normally held in engagement auf titulo' I Hi8.'

@@@IGIII limiti by spring 39 but may be disconnected by bell crank 49 which is actuated by inward movement of shaft 29. The shaft 29 carries a hub having two grooves 4| and 42 which are selectively engaged by a locking pin 43 which is normally held in the groovesv by spring 44 acting against the wall of the casing 45 of the instrument, a section of which is shown. The pin 43 may be withdrawn by knob 46 when it is desired to shift the shaft 29. In the outer position of shaft 29, as shown, the clutch 31 is engaged. When shaft 29 is shifted to its inner position the locking pin 43 engages groove 42 and the bell crank 49 disconnects the clutch 31.

The gear 38 meshes with a gear 41 on shafting 48 which is connected to move a time-speed chart 49 through gears 59 and racks 5I. The chart 49 is mounted to be moved vertically relative to a reference wire 52 by guides (not shown). The ends of the reference wire 52 are secured to the casing 45, portions only of which are shown. A pair of springs 53 connect the lower edge of the chart 49 to the casing by pins 54 and tend to bring the chart 49 against the fixed stops 55 secured to the casing 45, portions of which are shown.

The time-speed chart 49 includes vertical equally spaced lines l56 which represent time or the abscissa as indicated by the time scale 51 across the upper portion of the chart. The chart 49 also has speed lines 58 so spaced that the ordinate or vertical movement from its zero position, required of the chart to bring the intersection of the speed line, representing the speed at which the target is approaching, and the time line 56, representing the length 0f the time of movement of the target, to the reference Wire 52 represents the distance traveled by a target at the speed and during the time represented by the intersection. The speeds represented by the speed lines 58 are indicated b'y the numerals along the righthand edge of the chart 49.

The wide face gear I2 is connected to a gear 59 which turns shaft -69 in accordance with the angular position of the vector arm 3. Shaft 69 has two branches, 6I and 62 respectively.

Branch 6| of shaft 69 terminates in one part 63 of a clutch 64, the other part 65 of the clutch 64 is slidably connected to shaft 66 which carries a horizontal deection dial 61, which is read against an index 68. The shaft `66 carries a centralizing cam 69 which cooperates with a roller 19 on an arm 1| pivoted on a pin 12. The roller 19 is forced against the cam 69 by a spring 13 connected to the arm 1| and a pin 14. The pins 12 and 14 are secured to a part of the casing 45.

Branch 62 of shaft 69 terminates in one part 15 of a clutch 16, the other part 11 of the clutch 16 is slidably connected to shaft 18 which carries a sight angle dial 19, which is read against an index 89. The shaft 18 carries a centralizing cam 8| which cooperates with a roller 82 on an arm 83 pivoted on a pin 84. The roller 82 is forced against the cam 8| by a spring 85 connected to the arm 83 and a pin 86. The pins 84 and 86 are secured to a part of the casing 45.

The part 65 of clutch 64 includes a grooved collar which is engaged by a pin 81 in a lever 88. One end of the lever 88 is pivoted on a bracket 89, secured to a part of the casing 45, and the other end is forced against the end of gear I3 on shaft I4 by means of a spring 99 acting against a collar 9| on shaft 66. The part 'I1 of clutch 16 similarly includes a grooved collar which is engaged by a pin 92 in a lever 93. One end of the lever 93 is pivoted on a bracklet 94, secured to a part of the casing 45, and the other end is forced against the end of gear I3 by means of a spring 95 acting against a collar 96 on shaft 18. Stops 91 and 98 are provided to limit the downward movement of levers 88 and 93 respectively when the gear I3 is shifted out of engagement with the ends of the levers.

The shaft I4 carries a collar having three grooves 99, |99 and |9| which cooperate with a locking pin |92 to hold shaft I4 in one of three positions of longitudinal movement. The looking pin |92 is forced into the grooves by a spring |93 acting against a collar |94 on pin |92 and against the casing 45. The pin may be withdrawn from engagement with the grooves 99, |99 and |9| by means of knob' |95 to permit longitudinal shifting of shaft I4.

In Fig. 2 the shaft I4 is shown in its innermost position with the clutches 64 and 16 Iboth held open by the levers 88 and 93 respectively. In Fig. 3 the shaft I4 is shown in its central position with clutch 64 held open by lever 88 and clutch 16 closed. In Fig. 4 the shaft I4 is shown in its outermost position with both clutches 64 and 16 closed.

Operation When a target is observed to be approaching, the knobs I5 and 28 are placed in their innermost position which releases the clutches 64, 16 and 31 so that the dials 61 and 19 are brought to their zero positions by the cams 69 and 8| and the time-speed chart 49 is brought to its zero position by the springs 53.

As soon as the position of the target is determined in terms of elevation angle and range or height, as for the point A of Fig. l, the vector arm 3 and the wires 22 and 23 are set by the knobs I5, 28 and 24 respectively to intersect at the point on the trajectory chart corresponding to the observed position A. The wire 23 will be in the position shown in Fig. 2 and the wire 22 and the arm 3 will be in the position shown by the dotted lines 22A and 3A respectively. A stopwatch or other timing means is started at the time of making the observations representing the position A.

The knob 28 is now shifted to its outer position which closes the clutch 31 thereby connecting the time-speed chart 4-9 to the component slide 4 for simultaneous movement. The knob 28 is rotated to move the chart l4'9 so'that the time line 56, representing the selected preparation period, and the speed line '58, representing the target speed, intersect under the reference wire 52. The movement of the chart 49 represents the movement of the target during the preparation period and the component slide 4 is moved to the left a corresponding amount so that the intersection of the wires 22 and 23 now represent the point B of Fig 1. The Wire 22 is in the position indicated by the dotted line 22B on Fig. 2. The vector arm 3 is next rotated by knob I5 till its graduated edge passes through this intersection, when it is in the position indicated by the line 3B on Fig. 2. The angular position of the vector arm 3 as read from the angular elevation scale 9 equals the angle A3 of Fig. 1 and the point at which the Wire 22, in its position 22B, crosses the horizontal range scale I6 represents the horizontal range BH3 of Fig. 1.

The knob 28 is now returned to its inner position which releases the clutch 31 and permits the time-speed chart 49 to return to its zero position, under the action of the springs 53. f

The knob 28 is next shifted to its outer position, which' reconnects the clutch 31, and the knob I is shifted to its intermediate position as shown in Fig. 3 thereby allowing the lever 93 to move down sufficiently to permit the spring 95 to close the clutch 16. The sight angle dial 19 is now rotatively connected to the knob I5.

The operator observes the time of flight to the point B from the time of flight curves 20 of the trajectory chart 6 and turns knob 28 to bring the time-speed chart 49 to the position corresponding to the time of flight and the target speed. As the chart 49 is moved the component slide 4 and the wire 22 move to the lefttoward the position representing the point C of Fig. l. As the Wire 22 approaches the position C as shown in Fig. 2 the operator observes from the trajectory chart B the time of flight for this shifting position and adjusts the time-speed chart 49 so that the corresponding time line 56 intersects the speed line 58 at the reference wire 52. The setting of the time-speed chart 49 as shown on Fig. 2 represents a target speed of two hundred miles per hour and a time of ten seconds. The wires 22 and 23 also intersect on the ten second time -of flight curve 20 of the trajectory chart 6. This operation has therefore determined the point C of Fig. 1.

The operator now turns the knob Il5 to bring the graduated edge of the vector arm 3 to the intersection of the wires 22 and 23 as indicated on Fig.'2 by the dotted line 3C. The angular position of the vector arm 3 as read from the elevation scale 9 now equals the angle A2 of Fig. 1, and the sight angle dial 19 will have been moved through the angle Ut, which equals A2- A3 as shown by Equation 7.

The knob I5 is now shifted to its outer position as shown in Fig. 4 thus allowing lever 88 to move sufficiently for the spring 90 to close the clutch 64 and thereby rotatively connect the deection dial 61 to the knob I5. The clutch 16 remains closed during this shift.

The operator now moves the vector arm 3, by the knob I5, until its graduated edge is tangent to the trajectory curve I9 which passes through the point C. The vector arm `3 is now in the position shown in Fig. 2 and the sight angle dial 19 has been moved an amount representing the super-elevation (e). The total movement of the dial 19 therefore indicates the sight angle (Us) or Ut-l-e as seen from Equation 8.

The' deflection dial 61 is moved by this last adjustment of the vector arm 3 an amount proportional to the super-elevation (e) which, as has been pointed out, is proportional to the horizontal deflection (Ds).

The readings of sight angle and deflection indicated by the dials 19 and 61 are set on the sights of the gun so that as the sights are maintained on the target the gun is in the proper po'- sition for firing at the end of the preparation period, that is, when the target is at the point B. The end of the preparation period may be determined from the stop-watch which was started when the observations of target position were made.

Fuse setting values may be obtained for the point C from the time of flight curves 20 of the trajectory chart 6 or by other well known means.

It is obvious that various changes may be made by those skilled in the art in the selection of mechanisms and the mode of operation. For exl vvention has been described as used for a target ap.

proaching at a substantially constant height it is contemplated that variations in height may be allowed for by appropriate adjustments of the height setting to agree with the actual height of the target at the successive computing points. It is also obvious that a multiplier may be provided for aiding in this adjustment similar to that provided for the horizontal range adjustment.

I claim:

1. Apparatus for use in aiming a gun, comprising a ballistic chart having curves representing the trajectory and the time of flight of a projectile relative to the gun, a vector analyzer associated with the chart including a vector arm and a pair of component slides, the vector arm having its axis of rotation located to intersect the point of the chart representing the gun and each component slide having an index movable over the chart, means operable to move one component slide to position its index relative to the chart in accordance with the height of a target, means operable to move the second component slide to position its index relative to the vchart in accordance with the horizontal range of the target, means operable to angularly position the vector arm relative to the chart in accordance with the angular position of the target corresponding to the intersection of the indices of the component slides, means for determining the product of time and target speed including a part movable in accordance with said product, and clutch means operable to connect the part to the means to move the second component slide, whereby operation of the means to move the second component slide will move the part and the second component slide simultaneously and in corresponding amounts.

2. Apparatus for use in aiming a gun, comprising a ballistic chart having curves representing the trajectory and the time of flight of a projectile relative to the gun, a vector analyzer associated with the chart including a vector arm and a pair ofv component slides, the vector arm having its axis of rotation located to intersect the point of the chart representing the gun and each component slide having an index movable over the to position its index relative to the chart in accordance with the horizontal range of the target, means operable to angularly position the vector arm relative to the chart in accordance with the angular position of the target corresponding to the intersection of the indices of the component s1ides,a time-distance chart having lines representing target speeds so spaced relative to rectangular coordinates that the abscissa and ordinate of a point represent time and distance traveled by the target at its respective speed, a

part movable to position representing ordinate corresponding to selected target speed and time values, and clutch means operable to connect the part to the means to move the second component slide, whereby operation of the means to move the second component slide will move the part and the second component slide simultaneously and in corresponding amounts.

GEORGE A. CROWTHER. 

